be surprised at 与 be surprised by 有无区别?
R.Quirk等在A Comprehensive Grammar of the English Language只是探讨了这两种结构的语法区别：
"I was surprised by their rejection of the offer. [1a]
I was surprised at their rejection of the offer. [1b]”
他们指出：“……也可在被动语态的句子中用 at 代替施动介词 by[1b]。这里的 at 表示感情反应及其刺激因素之间的关系。这一语境中的 surprised 是分词型形容词（它前面可以加 very）。”(§9.63)
但是他们没有分析这两种结构的语义区别。F. T. Wood 则提到了这两种结构的语义区别。他说：“当 surprised 作“被吓一跳”“大吃一惊”或“突然被捉”(taken by surprise) 解时，其后跟介词 by。当 surprised 作“充满惊奇”(filled with surprise) 时，其后跟介词 at。”
下面的例句有助于理解这两种结构的语法差别和语义差别：
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I am surprised at your behaviour. (COD) 我对你的行为深感惊异。
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I am very surprised at you. (Close) 看到你使我很惊讶。
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We were surprised at finding the house empty. (ALD) 我们发现这屋子空无一人，十分惊异。
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I am not surprised at your misunderstanding me. (Shaw) 对于你对我的误解,我并不感到惊奇。
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The thief was surprised by a knock on the door and jumped out of the window. (Alexander et al) 小偷被敲门声吓了一跳，从窗户跳了出去。
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Since none of the polls had predicted the winner, everyone was surprised by the result of the election.
A. astounded B. delighted C. encouraged D. perturbed (TOEFL)